TY - JOUR

T1 - BSD2 is a Rubisco-specific assembly chaperone, forms intermediary hetero-oligomeric complexes, and is nonlimiting to growth in tobacco

AU - Conlan, B.

AU - Birch, R.

AU - Kelso, C.

AU - Holland, S.

AU - De Souza, A.P.

AU - Long, S.P.

AU - Beck, J.L.

AU - Whitney, S.M.

PY - 2019/4/1

Y1 - 2019/4/1

N2 - The folding and assembly of Rubisco large and small subunits into L 8 S 8 holoenzyme in chloroplasts involves many auxiliary factors, including the chaperone BSD2. Here we identify apparent intermediary Rubisco-BSD2 assembly complexes in the model C 3 plant tobacco. We show BSD2 and Rubisco content decrease in tandem with leaf age with approximately half of the BSD2 in young leaves (~70 nmol BSD2 protomer.m 2 ) stably integrated in putative intermediary Rubisco complexes that account for <0.2% of the L 8 S 8 pool. RNAi-silencing BSD2 production in transplastomic tobacco producing bacterial L 2 Rubisco had no effect on leaf photosynthesis, cell ultrastructure, or plant growth. Genetic crossing the same RNAi-bsd2 alleles into wild-type tobacco however impaired L 8 S 8 Rubisco production and plant growth, indicating the only critical function of BSD2 is in Rubisco biogenesis. Agrobacterium mediated transient expression of tobacco, Arabidopsis, or maize BSD2 reinstated Rubisco biogenesis in BSD2-silenced tobacco. Overexpressing BSD2 in tobacco chloroplasts however did not alter Rubisco content, activation status, leaf photosynthesis rate, or plant growth in the field or in the glasshouse at 20°C or 35°C. Our findings indicate BSD2 functions exclusively in Rubisco biogenesis, can efficiently facilitate heterologous plant Rubisco assembly, and is produced in amounts nonlimiting to tobacco growth.

AB - The folding and assembly of Rubisco large and small subunits into L 8 S 8 holoenzyme in chloroplasts involves many auxiliary factors, including the chaperone BSD2. Here we identify apparent intermediary Rubisco-BSD2 assembly complexes in the model C 3 plant tobacco. We show BSD2 and Rubisco content decrease in tandem with leaf age with approximately half of the BSD2 in young leaves (~70 nmol BSD2 protomer.m 2 ) stably integrated in putative intermediary Rubisco complexes that account for <0.2% of the L 8 S 8 pool. RNAi-silencing BSD2 production in transplastomic tobacco producing bacterial L 2 Rubisco had no effect on leaf photosynthesis, cell ultrastructure, or plant growth. Genetic crossing the same RNAi-bsd2 alleles into wild-type tobacco however impaired L 8 S 8 Rubisco production and plant growth, indicating the only critical function of BSD2 is in Rubisco biogenesis. Agrobacterium mediated transient expression of tobacco, Arabidopsis, or maize BSD2 reinstated Rubisco biogenesis in BSD2-silenced tobacco. Overexpressing BSD2 in tobacco chloroplasts however did not alter Rubisco content, activation status, leaf photosynthesis rate, or plant growth in the field or in the glasshouse at 20°C or 35°C. Our findings indicate BSD2 functions exclusively in Rubisco biogenesis, can efficiently facilitate heterologous plant Rubisco assembly, and is produced in amounts nonlimiting to tobacco growth.

KW - chaperone

KW - photosynthesis

KW - protein folding

KW - RuBP carboxylation

KW - bacterium

KW - biochemical composition

KW - chloroplast

KW - enzyme

KW - enzyme activity

KW - gene expression

KW - genetic engineering

KW - growth

KW - limiting factor

KW - polymer

KW - protein

KW - tobacco

KW - ultrastructure

KW - Agrobacterium

KW - Arabidopsis

KW - Bacteria (microorganisms)

KW - Nicotiana tabacum

KW - Zea mays

U2 - 10.1111/pce.13473

DO - 10.1111/pce.13473

M3 - Journal article

VL - 42

SP - 1287

EP - 1301

JO - Plant, Cell and Environment

JF - Plant, Cell and Environment

SN - 0140-7791

IS - 4

ER -